(57) The primary winding (60) of a displacement transducer (40) is energised by turning
on a transistor (Q2) when a flip-flop (166) has been reset to turn off a transistor
(Q3), in response to a pulse (A) from a pulse generator (150). The transistor (Q2)
does not turn on until the pulse has terminated and thereby turned off another transistor
(Q1). The current builds up until a comparator (164) sets the flip-flop (166) to turn
on Q3 and thereby turn off Q2. In order to prevent overdriving a controlled device,
the smoothed output (Vo1, Vo2) from each secondary winding (82, 84) is applied to
a corresponding comparator (168, 170), either of which, when a predetermined threshold
is overstepped, turns on Q1, (to turn off Q2), via a comparator (156) and prevents
the flip-flop (166) being reset via a comparator (158).
|
|
